1. Field of the Invention
The present invention is directed to a microelectronic component of the type using a quantum mechanical effect.
2. Description of the Prior Art
Microelectronic components wherein a quantum-mechanical effect is utilized are acquiring significance in view of the development of extremely fast LSI electronic components. Interest in the field is directed, among other things, to the effect of the Coulomb blockade that is described in K. K. Likharev, Granular Nanoelectronics, D. K. Ferry editor, Plenum, New York (1991) pages 371 ff.
The Coulomb blockade arises because the energy of the overall system changes when an electron tunnels through a tunnel contact. A tunnel contact is a structure that comprises two electrodes separated by an insulating layer, with the insulating layer being so thin that a tunnelling of individual electrons through the insulating layer occurs. The energy modification of the overall system lies on the q.sub.e.sup.2 /C order of magnitude of wherein q.sub.e is the charge of an electron and C is the capacitance of the tunnel contact. When this energy modification is an energy elevation clearly above the thermal energy of the system k.sub.B T, wherein k.sub.B is the Boltzmann constant and T is the absolute temperature, then a tunnelling of the electron through the tunnel contact does not occur. The current through the tunnel contact is thus blocked. When, by contrast, the energy modification lies on the order of or is below the thermal energy, i.e. q.sub.e.sup.2 /C.ltoreq.k.sub.B T, then a tunnelling of an electron over the tunnel contact can occur.
The utilization of the Coulomb blockade is therefore possible given structures in the range of 30 through 100 nm that are operated in the millikelvin range (see, for example, E. Gladun et al, Physik in unserer Zeit, Vol. 23 (1992), pages 159 ff and L. J. Geerligs et al, Phys. Rev. Lett., Vol. 65 (1990), pages 3030 ff) or given structures having a size clearly below 10 nm that are operated at higher temperatures (see, for example, C. Schoenenberger et al, Europhys. Lett., Vol. 20 (1992), pages 249 ff).
For example, two electrodes of aluminum are employed in the tunnel contact in the former instance, a thin oxide layer being arranged between these two electrodes (see A. Gladun et al, Physik in unserer Zeit, Vol. 23 (1992), pages 159 ff). Such a Coulomb blockade component is only functional at extremely low temperatures. The electrical properties of this tunnel contact can be set via a scaling of the components.
According to an estimate made based on the energy modification and thermal energy, the Coulomb blockade effect only occurs at room temperature given elements having a tunnel contact with a capacitance of 10.sup.-18 F or below. Such elements have an expanse on the order of magnitude of a few nanometers.
The contacting of such small elements ensues with the assistance of scanning microscopes such as the scanning tunnelling microscope or the atomic power microscope (see C. Schoenenberger et al, Europhys. Lett., Vol. 20 (1992), pages 249 ff). Other possibilities of contacting elements on this order of magnitude are not known.
Metal clusters that are surrounded by an insulating sheath have been proposed as tunnel contact elements having nanometer size (see German OS 42 12 220). The electrical properties of these tunnel contact elements are determined by the size and the nature of the metal clusters as well as by the insulating sheathes.
In German OS 42 12 220, microelectrodes, i.e. scanning microscopes, are employed for contacting individual tunnel elements. Such a contacting is in fact expedient for testing and scientific examination of such tunnel elements; it is unsuitable, however, for the employment of the tunnel elements as a microelectronic component within a complex circuit arrangement.
It is disclosed as a practical embodiment in German OS 42 12 220 to accept the individual elements in a receptacle mount as a fill and to correspondingly contact them via the receptacle mount, or to form a pressed member by compressing the individual elements under high pressure, this pressed member being provided with contacts. Component members are formed in this way as a wafer having a diameter of 5 mm and a thickness of 0.379 mm. Dimensions of 2 through 10 mm for the diameter and 0.1 through 1 mm for the thickness are preferred. Such components have a cut-off voltage on the order of magnitude of kilovolts, which is unbeneficial for employment in microelectronics.